20-gear double-overspeed mechanical automatic transmission

Abstract

The utility model discloses a 20-gear double-overspeed mechanical automatic transmission, and belongs to the field of heavy truck transmissions. The transmission provided by the utility model adopts a '2X5X2' type three-section structure, the front auxiliary box has two gears, the main box has five gears, and the rear auxiliary box has high and low gears, so that 20 gears are realized through cooperative work, the transmission has wider total speed ratio and smaller stage difference, and stable gear shifting and excellent performance can be realized; the transmission is provided with two overgears with different speed ratios, the minimum speed ratio can reach about 0.7, the requirement for rapid driving is met, different overgears are selected according to different use working conditions, the maneuverability of the transmission is improved, and the economical efficiency of the whole vehicle is improved.

Description

Technical Field

[0001] This utility model relates to the field of heavy-duty truck transmission technology, and in particular to a 20-speed dual overspeed mechanical automatic transmission. Background Technology

[0002] With the continuous development of the commercial vehicle market, the performance requirements for transmissions are also increasing. Automatic manual transmissions (AMTs) combine the high transmission efficiency of manual transmissions with the low cost of automatic transmissions, and have been gradually adopted in the commercial vehicle market. In the heavy-duty commercial vehicle market, especially under heavy loads and complex operating conditions, commercial vehicles require more gears to adapt to different driving speeds and torque demands. At the same time, with the increasing number of high-horsepower engines, it is necessary to develop high-torque transmissions to match them and meet the power requirements of commercial vehicles during starting, acceleration, and hill climbing. Therefore, how to optimize transmission design to meet the demands of high loads and high torque while improving transmission efficiency and reducing costs has become an urgent problem to be solved. Utility Model Content

[0003] To address the problems of insufficient gear quantity, low transmission efficiency, and inability to meet high torque requirements in existing transmissions, this invention provides a 20-speed dual-overspeed mechanical automatic transmission. This mechanical automatic transmission can optimize performance under heavy loads and complex operating conditions, meeting the needs of commercial vehicles for multi-gear, high efficiency, and high torque transmission.

[0004] To achieve the above objectives, this utility model provides the following technical solution:

[0005] This utility model provides a 20-speed dual overspeed mechanical automatic transmission, including a primary shaft, a secondary shaft, and an auxiliary gearbox main shaft;

[0006] A first shaft passes through the clutch housing and extends into the transmission housing. Inside the transmission housing, a first-shaft speed measuring disc, a first-shaft distribution gear, a front auxiliary gearbox synchronizer, and a first-shaft drive gear are sequentially mounted on this first shaft. A second shaft is located inside the transmission housing, and sequentially mounted on it are a fourth- and fifth-speed sliding sleeve, a second-shaft fifth-speed gear, a second-shaft third-speed gear, a second- and third-speed sliding sleeve, a second-shaft second-speed gear, a second-shaft first-speed gear, a first-reverse sliding sleeve, and a second-shaft reverse gear. A first intermediate shaft and a second intermediate shaft are respectively located on either side of the first and second shafts inside the transmission housing. The second intermediate shaft is sequentially equipped with an intermediate shaft speed-distributing gear that meshes with the first shaft speed-distributing gear, an intermediate shaft transmission gear that meshes with the first shaft drive gear, an intermediate shaft fifth gear that meshes with the second shaft fifth gear, an intermediate shaft third gear that meshes with the second shaft third gear, an intermediate shaft second gear that meshes with the second shaft second gear, an intermediate shaft first gear that meshes with the second shaft first gear, and an intermediate shaft reverse gear; the intermediate shaft reverse gear meshes with a reverse gear interlocking wheel, which is mounted on the reverse intermediate shaft, and the reverse gear interlocking wheel and the second shaft reverse gear are constantly meshed;

[0007] One end of the two shafts extends into the rear cover housing. A secondary gearbox drive gear is installed at the end of the two shafts inside the rear cover housing. A secondary gearbox main shaft is installed inside the rear cover housing. A secondary gearbox synchronizer and a secondary gearbox main shaft reduction gear are installed sequentially on the secondary gearbox main shaft. A secondary gearbox intermediate shaft is symmetrically arranged on both sides of the two shafts and the secondary gearbox main shaft inside the rear cover housing. A secondary gearbox transmission gear that meshes with the secondary gearbox drive gear and a secondary gearbox low gear that meshes with the secondary gearbox main shaft reduction gear are installed on the secondary gearbox intermediate shaft.

[0008] The second intermediate shaft extends into the clutch housing, and a brake is provided at the end of the second intermediate shaft in the clutch housing.

[0009] The auxiliary gearbox transmission gear and the auxiliary gearbox low gear are integrated on the auxiliary gearbox intermediate shaft, forming an integral shaft and gear structure with the auxiliary gearbox intermediate shaft.

[0010] The inner rings of the two-shaft fifth gear, two-shaft third gear, two-shaft second gear, two-shaft first gear, and two-shaft reverse gear are all equipped with gear spline washers, and the gear spline washers are engaged with the two shafts through splines.

[0011] The intermediate shaft first gear and intermediate shaft reverse gear are integrated on the second intermediate shaft, forming an integral shaft and gear structure with the second intermediate shaft.

[0012] The intermediate shaft speed-dividing gear, intermediate shaft transmission gear, intermediate shaft fifth gear, intermediate shaft third gear, and intermediate shaft second gear are respectively fixed to the first intermediate shaft or the second intermediate shaft by cylindrical pins.

[0013] The auxiliary gearbox drive gear is fixedly connected to the end of the two shafts inside the rear cover housing via a spline, and the auxiliary gearbox main shaft reduction gear is set on the auxiliary gearbox main shaft via a spline shim, and can float on the auxiliary gearbox main shaft.

[0014] The fourth and fifth gear sliding sleeves, the second and third gear sliding sleeves, and the first reverse gear sliding sleeve are engaged with the two shafts via splines.

[0015] The first-shaft gear, first-shaft transmission gear, second-shaft fifth-speed gear, second-shaft third-speed gear, second-shaft second-speed gear, second-shaft first-speed gear, second-shaft reverse gear, auxiliary gearbox drive gear, auxiliary gearbox main shaft reduction gear, intermediate shaft gear, intermediate shaft transmission gear, second intermediate shaft, intermediate shaft fifth-speed gear, intermediate shaft third-speed gear, intermediate shaft second-speed gear, intermediate shaft first-speed gear, reverse gear, intermediate shaft reverse gear, auxiliary gearbox transmission gear, and auxiliary gearbox low-speed gear all adopt helical gears.

[0016] A flange is provided at one end of the auxiliary housing main shaft that extends out of the rear cover housing.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0018] This utility model provides a 20-speed dual overdrive mechanical automatic transmission, employing a "2X5X2" three-stage structure. It offers 20 gears, providing a wider total gear ratio range, enabling the vehicle to adapt to a wider range of driving conditions and maintaining smooth shifting, avoiding the jerking sensation that can occur with traditional transmissions. The transmission provides two different overdrive gears with a minimum gear ratio of 0.7, meeting the needs of high-speed driving. Simultaneously, the smaller gear difference improves the transmission's maneuverability, allowing selection of the appropriate overdrive gear under different operating conditions, thus enhancing the vehicle's economy and power performance. The transmission achieves "power splitting" through an optimized structure, transmitting greater torque within the same volume, thereby improving the vehicle's power output and adapting to various driving needs. This transmission effectively improves shift smoothness, economy, torque capacity, and power output, providing better support for the vehicle's performance and the versatility of its operating conditions.

[0019] Furthermore, both the main and auxiliary gearboxes adopt helical gears and a double intermediate shaft structure. This design not only reduces manufacturing costs, but also reduces the requirements for machining and assembly precision by using a "floating" two-shaft assembly, so that the transmission can reduce production complexity and cost while ensuring high performance.

[0020] Furthermore, the intermediate shaft drive gear and low-gear of the rear auxiliary gearbox are integrated into a single shaft structure, which can withstand greater torque compared to the commonly used interference fit and welding process. This allows the transmission to better adapt to high torque conditions and meet high power requirements. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the 20-speed dual overspeed mechanical automatic transmission of this utility model;

[0023] Figure 2 This is a schematic diagram of the intermediate shaft and reverse gear structure of this utility model;

[0024] Figure 3 This is a schematic diagram of the integrated shaft structure of the intermediate shaft of the rear auxiliary box of this utility model;

[0025] The components include: 1. Shaft 1; 2. Shaft 1 speed measuring disc; 3. Shaft 1 speed distribution gear; 4. Front and auxiliary gearbox synchronizer; 5. Shaft 1 transmission gear; 6. First intermediate shaft; 7. Fourth and fifth gear sliding sleeves; 8. Second shaft 2 fifth gear; 9. Second shaft 2 third gear; 10. Second and third gear sliding sleeves; 11. Second shaft 2 second gear; 12. Second shaft 2 first gear; 13. First reverse gear sliding sleeve; 14. Second shaft 2 reverse gear; 15. Auxiliary gearbox drive gear; 16. Auxiliary gearbox synchronizer; 17. Auxiliary gearbox main shaft reduction gear. ; 18. Flange; 19. Intermediate shaft speed divider gear; 20. Intermediate shaft drive gear; 21. Second intermediate shaft; 22. Intermediate shaft fifth gear; 23. Intermediate shaft third gear; 24. Second shaft; 25. Intermediate shaft second gear; 26. Intermediate shaft first gear; 27. Reverse gear; 28. Intermediate shaft reverse gear; 29. ​​Auxiliary gearbox intermediate shaft; 2901. Auxiliary gearbox drive gear; 2902. Auxiliary gearbox low gear; 30. Brake; 31. Auxiliary gearbox main shaft. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0029] In the description of the embodiments of this utility model, it should be noted that the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the utility model product is in use. These are merely for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the utility model. Furthermore, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of the embodiments of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] The present invention will be further described below with reference to the accompanying drawings:

[0033] In response to the future development trend of automatic transmissions, this utility model provides a 20-speed dual overdrive mechanical automatic transmission. It adopts an integrated design with 20 forward gears, including two overdrive gears. It features the characteristics of transmitting greater torque, a wider speed ratio range, smaller speed ratio differences, higher fuel economy, and higher reliability, meeting the needs of the future heavy-duty commercial vehicle market.

[0034] like Figure 1As shown, this embodiment provides a 20-speed dual-overspeed mechanical automatic transmission, including a clutch housing, a transmission housing, and a rear cover housing. From the input end to the output end, a primary shaft 1, a secondary shaft 24, and an auxiliary gearbox main shaft 31 are arranged sequentially. The front auxiliary gearbox includes a primary shaft 1, a primary shaft speed measuring disc 2, a primary shaft distribution gear 3, a front auxiliary gearbox synchronizer 4, a primary shaft drive gear 5, an intermediate shaft distribution gear 19, and an intermediate shaft drive gear 20. The primary shaft 1 penetrates the clutch housing and extends into the transmission housing. On the primary shaft 1 within the transmission housing, the primary shaft speed measuring disc 2, the primary shaft distribution gear 3, the front auxiliary gearbox synchronizer 4, and the primary shaft drive gear 5 are arranged sequentially. The primary shaft drive gear 5 also serves as the primary shaft's fourth gear. Gears; the main housing includes two shafts, gears and sleeves mounted on the two shafts. The second shaft 24 is sequentially equipped with a fourth and fifth gear sleeve 7, a fifth gear 8, a third gear 9, a second and third gear sleeve 10, a second gear 11, a first gear 12, a first reverse gear sleeve 13, and a reverse gear 14. The second shaft 24 is equipped with external splines. The inner rings of the fifth gear 8, third gear 9, second gear 11, first gear 12, and reverse gear 14 are all equipped with gear spline washers. The gear spline washers are equipped with internal splines that mesh with the external splines of the second shaft, making these gears "floating" on the second shaft and restricting their axial movement. The fourth and fifth gear sliding sleeves 7, the second and third gear sliding sleeves 10, and the first and reverse gear sliding sleeves 13 are all equipped with internal splines. Each sliding sleeve engages with the external splines on the second shaft 24 through the internal splines. Each sliding sleeve can move axially on the second shaft 24 and can transmit torque through the splines.

[0035] A first intermediate shaft 6 and a second intermediate shaft 21 are respectively arranged on both sides of the primary shaft 1 and the secondary shaft 24 inside the transmission housing. The first intermediate shaft 6 and the second intermediate shaft 21 are symmetrically arranged on both sides of the primary shaft 1 and the secondary shaft 24 inside the transmission housing, and the central axes of the first intermediate shaft 6, the second intermediate shaft 21, the primary shaft 1, and the secondary shaft 24 are coplanar. On both the first intermediate shaft 6 and the second intermediate shaft 21, there are sequentially arranged an intermediate shaft distribution gear 19 that meshes with the primary shaft distribution gear 3, an intermediate shaft drive gear 20 that meshes with the primary shaft drive gear 5, an intermediate shaft fifth gear 22 that meshes with the secondary shaft fifth gear 8, an intermediate shaft third gear 23 that meshes with the secondary shaft third gear 9, and a... The intermediate shaft second gear 25 meshes with the second gear 11 of the second shaft, the intermediate shaft first gear 26 meshes with the first gear 12 of the second shaft, and the intermediate shaft reverse gear 28 does not directly mesh with the second shaft reverse gear 14. The intermediate shaft drive gear 20 is also the intermediate shaft fourth gear. The intermediate shaft distribution gear 19, intermediate shaft drive gear 20, intermediate shaft fifth gear 22, intermediate shaft third gear 23, and intermediate shaft second gear 25 are fixed to the first intermediate shaft 6 or the second intermediate shaft 21 by cylindrical pins. All gears on the first intermediate shaft 6 or the second intermediate shaft 21 rotate with the corresponding first intermediate shaft 6 or second intermediate shaft 21. The intermediate shaft reverse gear 28 is constantly meshed with the reverse gear intermediate wheel 27, which is set on the reverse intermediate shaft. The reverse gear intermediate wheel 27 is constantly meshed with the second shaft reverse gear 14. The second intermediate shaft 21 extends into the clutch housing, and a brake 30 is set at the end of the second intermediate shaft 21 in the clutch housing.

[0036] The rear auxiliary gearbox includes an auxiliary gearbox drive gear 15, an auxiliary gearbox synchronizer 16, an auxiliary gearbox main shaft 31, an auxiliary gearbox main shaft reduction gear 17, and an auxiliary gearbox intermediate shaft 29. A second shaft 24 extends into the rear cover housing. The auxiliary gearbox drive gear 15 is installed at the end of the second shaft 24 within the rear cover housing. The auxiliary gearbox main shaft 31 is located within the rear cover housing. The auxiliary gearbox synchronizer 16 and the auxiliary gearbox main shaft reduction gear 17 are sequentially installed on the auxiliary gearbox main shaft 31. The auxiliary gearbox intermediate shaft 29 is symmetrically arranged on both sides of the second shaft 24 and the auxiliary gearbox main shaft 31 within the rear cover housing. The central axes of the auxiliary gearbox main shaft 31 and the auxiliary gearbox intermediate shaft 29 are coplanar. The auxiliary gearbox intermediate shaft 29 is equipped with an auxiliary gearbox transmission gear 2901 that meshes with the auxiliary gearbox drive gear 15 and an auxiliary gearbox low-gear gear 2902 that meshes with the auxiliary gearbox main shaft reduction gear 17. The auxiliary gearbox drive gear 15 is fixedly connected to the end of the second shaft 24 inside the rear cover housing via a spline and rotates together with the second shaft 24. The auxiliary gearbox main shaft reduction gear 17 is mounted on the auxiliary gearbox main shaft 31 via a spline washer and can float on the auxiliary gearbox main shaft 31. When the auxiliary gearbox synchronizer 16 slides forward to engage the auxiliary gearbox drive gear 15, a high gear is obtained; when the auxiliary gearbox synchronizer 16 slides backward to engage the auxiliary gearbox main shaft reduction gear 17, a low gear is obtained.

[0037] In some embodiments, such as Figure 2As shown, the intermediate shaft first gear 26 and intermediate shaft reverse gear 28 are integrated on the second intermediate shaft 21. The intermediate shaft first gear 26, intermediate shaft reverse gear 28 and the second intermediate shaft 21 form an integral shaft gear structure, which is convenient for processing and can transmit greater torque.

[0038] In some embodiments, such as Figure 3 As shown, the auxiliary gearbox transmission gear 2901 and the auxiliary gearbox low-gear 2902 are integrated on the auxiliary gearbox intermediate shaft 29, forming an integral shaft and gear structure with the auxiliary gearbox intermediate shaft 29. Unlike the commonly used interference fit and welding process, this method can transmit greater torque and meet high torque requirements.

[0039] The automatic transmission provided in this embodiment adopts a "2X5X2" cylindrical structure consisting of a front auxiliary gearbox, a main gearbox, and a rear auxiliary gearbox. The front auxiliary gearbox has 2 gears, the main gearbox has 5 gears, and the rear auxiliary gearbox has high and low gears. Through their coordinated operation, a total of 20 gears are achieved. These 20 gears provide a wider overall gear ratio and smaller gear intervals, enabling smooth shifting and excellent performance.

[0040] All gears in both the main and auxiliary gearboxes are helical gears. Both gearboxes employ a double intermediate shaft structure, with the intermediate shafts using a double-gear transmission for speed sharing. During power transmission, the synchronizer 4 on one shaft switches the gear on the first shaft to mesh with the corresponding gear on the intermediate shaft, transmitting power to the two intermediate shafts via a specific set of meshing gears, thus driving the rotation of the two intermediate shafts. The main gearbox's two-shaft assembly is in a "floating" state, which significantly reduces the machining and assembly precision required for the two-shaft assembly, reduces manufacturing costs, and enables "power splitting," allowing a larger torque to be transmitted within the same gearbox volume.

[0041] It has two overdrive gears with different speed ratios, with the minimum speed ratio reaching about 0.7, to meet the needs of high-speed driving. Different overdrive gears can be selected according to different operating conditions to improve the transmission's maneuverability and enhance the overall vehicle economy.

[0042] This transmission can be arranged in the same way and can be designed as a transmission assembly with a direct drive (minimum gear ratio of 1), one overdrive (one gear with a gear ratio less than 1), or two overdrive (two gears with a gear ratio less than 1).

[0043] On the first intermediate shaft 6 and the second intermediate shaft 21, the reverse gear and the first gear are adjusted to have the same parameters and are made into shaft teeth. The intermediate neutral position is no longer reserved separately, but is integrated with the first and reverse gears. This facilitates overall machining and strengthens the gears to meet the requirements of a high-torque transmission.

[0044] The transmission internally incorporates a forced lubrication oil pump structure and a power take-off (PTO) connection structure.

[0045] This embodiment describes a method for operating a 20-speed dual-overspeed mechanical automatic transmission, including:

[0046] Taking first gear as an example, the power transmission route of this utility model is explained as follows: When the transmission is engaged in first gear, the front auxiliary gearbox synchronizer 4 moves forward and meshes with the first shaft gear 3. The reverse gear sleeve 13 in the main gearbox slides forward, and the external spline on the sleeve meshes with the internal spline on the gear ring of the second shaft first gear 12. Power is input from the first shaft 1, and then transmitted to the intermediate shaft gear 19 on the left and right intermediate shafts through the front auxiliary gearbox synchronizer 4 and the first shaft gear 3, thus transmitting power from the first shaft to the intermediate shaft. This drives the left and right intermediate shafts to rotate, and the first gear 26 of the intermediate shaft also rotates with the intermediate shaft. The power is transmitted to the second shaft 24 through the first gear 26 of the intermediate shaft and the second shaft first gear 12 of the second shaft. The second shaft first gear 12 engages with the external spline of the first reverse gear sleeve 13 through the internal spline of the gear ring, and transmits the power to the first reverse gear sleeve 13. The first reverse gear sleeve 13 is connected to the second shaft 24 through the spline. Thus, the power transmitted from the first shaft 1 is transmitted to the second shaft 24 through the shifting mechanism, and the main gearbox completes the shifting.

[0047] Since first gear is the low gear range, the auxiliary gearbox is connected to the low gear range. At this time, the auxiliary gearbox synchronizer 16 slides backward and engages with the auxiliary gearbox main shaft reduction gear 17. The power transmitted from the second shaft 24 is transmitted to the auxiliary gearbox main shaft 31 through the auxiliary gearbox drive gear 15, the auxiliary gearbox intermediate shaft 29, the auxiliary gearbox main shaft reduction gear 17, and the auxiliary gearbox synchronizer 16, and then output through the flange 18 to complete the power transmission.

[0048] The power transmission is similar in other gears. When the transmission is in a high gear, the auxiliary gearbox synchronizer 16 is mainly slid forward to engage with the auxiliary gearbox drive gear 15, and at the same time, the appropriate gear on the shaft is selected to engage according to the gear.

[0049] like Figure 1 As shown, this transmission has two overdrive gears. Unlike conventional transmissions, when the gears are arranged axially, the fourth and fifth gears are interchanged. At the same time, when power is transmitted from the fifth gear 22 on the intermediate shaft to the fifth gear 8 on the second shaft, it has an acceleration effect (gear ratio greater than 1). When the power is transmitted from the first shaft to the intermediate shaft, it has a deceleration effect (gear ratio greater than 1), thus achieving the purpose of having two overdrive gears.

[0050] The above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although the utility model has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of this utility model. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model are within the protection scope of the claims of this utility model pending approval.

Claims

1. A 20-speed dual-overspeed mechanical automatic transmission, characterized in that, It includes a primary shaft (1), a secondary shaft (24), and a secondary main shaft (31); A shaft (1) passes through the clutch housing and extends into the transmission housing. A shaft speed measuring disc (2), a shaft distribution gear (3), a front auxiliary gearbox synchronizer (4), and a shaft transmission gear (5) are sequentially mounted on the shaft inside the transmission housing. A second shaft (24) is located inside the transmission housing. A fourth and fifth gear sliding sleeve (7), a second shaft fifth gear (8), a second shaft third gear (9), a second and third gear sliding sleeve (10), a second shaft second gear (11), a second shaft first gear (12), a first reverse gear sliding sleeve (13), and a second shaft reverse gear (14) are sequentially mounted on the second shaft (1) and the second shaft (24). A first intermediate shaft (6) and a second intermediate shaft (21) are respectively mounted on both sides of the shaft (1) and the second shaft (24) inside the transmission housing. The first intermediate shaft (6) and the second intermediate shaft (21)... The intermediate shaft (21) is sequentially provided with an intermediate shaft speed distribution gear (19) meshing with the first shaft speed distribution gear (3), an intermediate shaft transmission gear (20) meshing with the first shaft transmission gear (5), an intermediate shaft fifth gear (22) meshing with the second shaft fifth gear (8), an intermediate shaft third gear (23) meshing with the second shaft third gear (9), an intermediate shaft second gear (25) meshing with the second shaft second gear (11), an intermediate shaft first gear (26) meshing with the second shaft first gear (12), and an intermediate shaft reverse gear (28); the intermediate shaft reverse gear (28) meshes with the reverse gear intermediate wheel (27), the reverse gear intermediate wheel (27) is provided on the reverse intermediate shaft, and the reverse gear intermediate wheel (27) and the second shaft reverse gear (14) are constantly meshed; One end of the two shafts (24) extends into the rear cover housing. The end of the two shafts (24) inside the rear cover housing is provided with a secondary gearbox drive gear (15). A secondary gearbox main shaft (31) is provided in the rear cover housing. A secondary gearbox synchronizer (16) and a secondary gearbox main shaft reduction gear (17) are sequentially provided on the secondary gearbox main shaft (31). A secondary gearbox intermediate shaft (29) is symmetrically provided on both sides of the two shafts (24) and the secondary gearbox main shaft (31) inside the rear cover housing. A secondary gearbox transmission gear (2901) meshing with the secondary gearbox drive gear (15) and a secondary gearbox low gear (2902) meshing with the secondary gearbox main shaft reduction gear (17) are provided on the secondary gearbox intermediate shaft (29).

2. The 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The second intermediate shaft (21) extends into the clutch housing, and a brake (30) is provided at the end of the second intermediate shaft (21) of the clutch housing.

3. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The auxiliary gearbox transmission gear (2901) and the auxiliary gearbox low gear (2902) are integrated on the auxiliary gearbox intermediate shaft (29), forming an integral shaft and gear structure with the auxiliary gearbox intermediate shaft (29).

4. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The inner rings of the two-shaft fifth gear (8), two-shaft third gear (9), two-shaft second gear (11), two-shaft first gear (12) and two-shaft reverse gear (14) are all provided with gear spline pads, and the gear spline pads are engaged with the two shafts (24) through splines.

5. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The intermediate shaft first gear (26) and intermediate shaft reverse gear (28) are integrated on the second intermediate shaft (21) to form an integral shaft and gear structure with the second intermediate shaft (21).

6. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The intermediate shaft speed-dividing gear (19), intermediate shaft transmission gear (20), intermediate shaft fifth gear (22), intermediate shaft third gear (23), and intermediate shaft second gear (25) are respectively fixed to the first intermediate shaft (6) or the second intermediate shaft (21) by cylindrical pins.

7. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The auxiliary gearbox drive gear (15) is fixedly connected to the end of the two shafts (24) inside the rear cover housing via a spline. The auxiliary gearbox main shaft reduction gear (17) is set on the auxiliary gearbox main shaft (31) via a spline shim and can float on the auxiliary gearbox main shaft (31).

8. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The fourth and fifth gear sliding sleeves (7), the second and third gear sliding sleeves (10) and the first reverse gear sliding sleeve (13) are engaged with the second shaft (24) via splines.

9. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, The first shaft speed-dividing gear (3), the first shaft transmission gear (5), the second shaft fifth gear (8), the second shaft third gear (9), the second shaft second gear (11), the second shaft first gear (12), the second shaft reverse gear (14), the auxiliary gearbox drive gear (15), the auxiliary gearbox main shaft reduction gear (17), the intermediate shaft speed-dividing gear (19), the intermediate shaft transmission gear (20), the second intermediate shaft (21), the intermediate shaft fifth gear (22), the intermediate shaft third gear (23), the intermediate shaft second gear (25), the intermediate shaft first gear (26), the reverse gear intermediate wheel (27), the intermediate shaft reverse gear (28), the auxiliary gearbox transmission gear (2901), and the auxiliary gearbox low gear (2902) are all helical gears.

10. A 20-speed dual-overspeed mechanical automatic transmission according to claim 1, characterized in that, A flange (18) is provided at one end of the auxiliary housing main shaft (31) extending out of the rear cover housing.

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